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Floating point calculation change depending on the compiler


By : Xinh Xinh
Date : October 16 2020, 11:12 PM
I wish this helpful for you On x86, usually most calculations happen with 80-bit quantities, unless otherwise forced to be double-precision. Most other architectures I know of do all calculations in double-precision (again, unless otherwise overridden).
I don't know if you're running Solaris on SPARC or x86, but if the former, then I highly suspect that to be the cause of the difference.
code :


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What is floating point speculation and how does it differ from the compiler's floating point model


By : Elias Mantouvalos
Date : March 29 2020, 07:55 AM
Hope that helps -fp-model influences how floating-point computations are carried out, and can change the numeric result (by licensing unsafe optimizations or by changing the precision at which intermediate results are evaluated).
-fp-speculation does not change the numerical results, but can effect what floating-point flags are raised by an operation (or what traps are taken if floating-point traps are enabled). 99.99% of programmers don't need care about these things, so you can probably run with the default and not worry about it.
code :
double foo(double x) {
    // lots of computation
    if (x >= 0) return sqrt(x);
    else return x;
}
double foo(double x) {
    const double sqrtx = sqrt(x);
    // lots of computation
    if (x >= 0) return sqrtx;
    else return x;
}

Scala - how to change compiler behavior (automatic conversion to floating point types)?


By : Com Man
Date : March 29 2020, 07:55 AM
wish help you to fix your issue You have only two possibilities here: promote to Double or widen to AnyVal. In the latter case, division isn't even defined, which is kind of useless. If you want to demand this behavior, you can explicitly specify the type:
code :
val y = List[AnyVal](3,2.0)
y.head match {
  case i: Int => println("Whew, it is still an int!")  // This is printed
  case _ => println("Bah, it messed up again")
}

ULP calculation floating-point


By : Team One
Date : March 29 2020, 07:55 AM
I hope this helps . I'm not sure Java has the possibility of aliasing to get the bit pattern of the floating point number (there is a close enough alternative, as the second part of the answer shows), but if it does, then e is the bits 23 through 30 (31 is sign) minus some constant (as in the wikipedia description of the format, it's 127 unless the number is subnormal) while n is fixed (in this case it's 23 bits, or 24 if it includes the implicit 1)
It's recommended you use a lib that does this job for you properly.
code :
float ulp(float x) {
    int repr;
    float next;
    if (Float.isNaN(x)) return Float.NaN; //special handling, to be safe
    repr = Float.floatToIntBits(x);
    x++; //will work correctly independently of sign
    next = Float.intBitsToFloat(repr)
    return next-x;
}

Compiler flags for enhancing the precision of intermediate floating-point calculation


By : kenrus
Date : March 29 2020, 07:55 AM
may help you . GCC
[Edit on observed behavior of gcc 4.8.4, where default behavior is the opposite to documentation]
code :
double mult(double x, double y) {
    return x * y;
}
gcc -mfpmath=387 -Ofast -o precision.s -S precision.c
mult:
  .LFB24:
    .cfi_startproc
    movsd   %xmm1, -8(%rsp)
    fldl    -8(%rsp)
    movsd   %xmm0, -8(%rsp)
    fldl    -8(%rsp)
    fmulp   %st, %st(1)
    fstpl   -8(%rsp)
    movsd   -8(%rsp), %xmm0
    ret
    .cfi_endproc

Floating point calculation with constants in C?


By : rhines61
Date : October 08 2020, 05:00 PM
help you fix your problem Yes, you can perform floating-point arithmetic with constants in expressions in C programs, and yes, the compiler will often reduce these expressions at compile time. The situation is almost the same as for integer constants. That is, your example
code :
if(a > (100 / 0.1))
if(a > (100 * 10))
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